Background

Oligodendrogliomas (ODs) are primary glial brain tumors that are divided into grade II and anaplastic grade III tumors (World Health Organization [WHO] criteria). Typically, they have an indolent course, and patients may survive for many years after symptom onset. Their good prognosis relative to other parenchymal tumors probably stems from inherently less aggressive biological behavior and a favorable response to chemotherapy, a recently discovered finding based on genetic characteristics.

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Pathophysiology

Oligodendrogliomas arise in the cerebral hemispheres and are distributed among the frontal, parietal, temporal, and occipital lobe, in approximately a 3:2:2:1 ratio. Rarely, they can arise in the cerebellum, brain stem, and spinal cord.
[1] They usually occur in the cerebral white matter and are very cellular, with uniform nuclei. They react with glial fibrillary acidic protein on immunostaining.

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Epidemiology

Frequency

United States

The incidence of oligodendrogliomas ranges from 5-19% of all intracranial tumors. The newer studies showed incidence of oligodendrogliomas to be around 25% of all gliomas. This may be explained by the improvements in the treatment of oligodendrogliomas, prompting neuropathologists to favor the diagnosis.

International

No difference in the incidence of oligodendroglioma exists worldwide.

Mortality/Morbidity

The morbidity and mortality profile for oligodendrogliomas is much better than for astrocytic tumors. However, it also depends on tumor location and pressure effects, as with any other intracranial lesion. The median survival from initial diagnosis of all low-grade oligodendrogliomas (LGOs) is 4-10 years, but it is only 3-4 years for anaplastic oligodendrogliomas.

Race

No difference exists among the races.

Sex

Oligodendrogliomas occur in both sexes, with a male-to-female predominance of 2:1.

Age

Oligodendrogliomas may be diagnosed at any age but occur most commonly in young and middle-aged adults, with a median age at diagnosis of 40-50 years. In children, only 6% of gliomas are diagnosed as oligodendrogliomas.